The invention relates to a locking system for a rotating joint according to the preamble of the appended claim 1.
For harvesting, working machines are known which move on a terrain by means of wheels. These include a harvester in which a harvesting device is provided at the end of a boom assembly, a so-called harvester head for cutting and felling a tree stem and sawing it to pieces of desired length. The sawn tree stems are collected with a loading apparatus, or a forwarder equipped with a grapple, and are transported in its load space. For example, a harvester working machine with articulated steering comprises two frame parts which are arranged, by means of a joint, to swivel in relation to each other around a vertical axis. A swivel base is mounted on the first frame part to swivel around a vertical axis and is equipped with a cabin and a boom assembly, a harvester head being mounted at the end of the boom assembly. The boom assembly can also be mounted on a separate swivel base, and the cabin can be stationary. The second frame is equipped with a power source and a pair of wheels. The first frame part normally comprises one or two pairs of wheels.
Another known forwarder, movable by means of wheels, is disclosed in Swedish patent publication 509 907 and comprises two frame parts connected to each other by means of a joint. One of the frame parts is equipped with a load space where the tree stems are collected from the ground by means of a loader, its boom assembly being normally also mounted to the front part of the second frame part. The first frame part is equipped with a cabin and a power source for the working machine. For improving movability on a terrain, the frame parts are arranged to be articulated by means of a rotating joint with respect to each other around an axis in the longitudinal direction of the frame. The turning movement is normally limited. In addition to this, the working machine is controlled by steering the frame parts around a vertical axis by means of cylinders.
At present, so-called combined machines are also known, combining the functions of a harvester and a forwarder. In one example, the working machine comprises two frame parts which can be swivelled around a longitudinal and vertical axis. Thus, the first frame part is equipped with a boom assembly and a cabin, for example on a joint swivel base, as well as a power source, and the second frame part is equipped with a space for the load. The second frame part is normally supported by two separate wheel shafts.
To maintain stability of the working machine, it must be possible to lock the rotating joint to prevent swivelling of the frame parts. Particularly when the boom assembly is used, for example upon loading, cutting and delimbing, the position is locked, wherein the weight of the second frame part is also utilized as a counterweight. The presented rotating joint normally comprises a circumferential bearing which is a single-row filling slot type bearing. The outer race and the inner race of the bearing are coupled to different frame parts. The frame part may also be equipped with a transverse joint, by means of which the rotating joint and the frame part swivel.
As known, the rotating joint is also equipped with separate brake plates which are locked by means of brake cylinders. The brake plates and the brake cylinders become large, and they must be placed outside the rotating joint, which considerably increases the size and weight of the rotating joint. Because of the mounting and size of the brake plate, rotation is often possible within allowed limits only, which restricts the movement of the frame parts. The joint can be equipped with e.g. an arch-like cogging where the cogs extend in the axial direction. The rotation movement is locked with a locking means movable in the radial movement and set in the cogging. For example, a separate cylinder structure for moving the locking means, operated by a pressurized medium, is often also large in size. However, particularly the locking force of a single locking means also causes an unnecessary and uneven torque between the outer and inner races of the circumferential bearing, stressing the circumferential bearing. Consequently, prior art lockings increase the size of joints and the stresses.
It is an aim of the present invention to eliminate the above-mentioned problems. To attain this purpose, the locking system according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1.
Using the invention, a considerably integrated and compact construction is achieved, wherein it can also be applied in various rotating joints which also comprise joints in the transverse direction. The locking system also makes it possible to rotate the frame parts with respect to each other without limits. A particular advantage is achieved in that in the locked position, the circumferential bearing of the rotating joint is not subjected to forces caused by the locking. In a preferred embodiment of the invention, another particular advantage is a large annular hydraulic space for the pressurized medium, wherein the required control pressures for maintaining even great locking forces can be kept reasonable. The number of separate hydraulic spaces can also be easily increased. One advantage is that external energy and the pressurized medium are only used when necessary for locking and for maintaining the locking, and that the locking will be automatically released, thanks to the design of the cogging. Another advantage is that the rest of the cogging can also be arranged in such a way that it will not cause locking or releasing forces, wherein the locking system can be easily moved. The hydraulic space and the cogging can be made annular, wherein a balanced loading and functionality of the rotating joint are achieved in all the rotating positions. Particularly the cylindrical, centrally placed parts of the locking system are easy to manufacture e.g. by lathing.